Left: IUE spectrum of STB in IRAS 0833 (black, solid line) fitted with an SB99 spectrum for an age of 5.5 Myr (dashed lines). The model has been reddened to account for the Galactic extinction, as well as for the intrinsic extinction assuming both an LMC law and E(B − V) = 0.15 (red), and the Cardelli extinction law with E(B − V) = 0.20 (green). Right: IUE spectrum is shown as in the left panel (black, solid line). A composite model (blue, dashed line) was obtained summing the starburst model (red) and an SB99 spectrum of a 1-Gyr-old population reddened similarly as the young burst model (magenta, dashed line). Near-UV and optical photometric fluxes from Östlin et al. (2009) are marked with green crosses.